This invention relates to disk drive systems, and more particularly, to an apparatus and method of securing one or more data storage disks to a hub of a spindle motor used in a disk drive.
Disk drive data storage systems typically include one or more data storage disks mounted to a spindle hub, and a spindle motor drives the spindle hub which rotates the disks at high RPMs. A disk clamp assembly secures the disks to the hub.
Data disks have a central bore or opening that receives the spindle hub. A common type of disk clamp assembly includes an annular or disk-shaped disk clamp, and a number of screws that secure the clamp to the hub. One or more disks positioned below the clamp are secured to the hub. In addition, spacers may be placed on both sides of each disk. For example, in a disk drive with a single data disk, the arrangement could include in series, a clamp, a spacer adjacent the clamp, a disk, a spacer on the opposite side of the disk, and then the hub. For some disk clamp assemblies, a top data disk may directly contact the disk clamp without the use of a spacer. The disks and spacers are often referred to as a disk pack.
Example of references disclosing clamps utilizing securing screws include the U.S. Pat. Nos. 5,274,517; 5,333,080; 5,528,434; and 5,790,345.
Certain disadvantages arise by using screws to secure the clamp to the hub. One distinct disadvantage is that the screws transmit uneven and irregular radially and axially directed forces to the data disk, thus resulting in surface irregularities on the disk. Any distortion or surface irregularities of the disk read/write surface may result in poor head transducer flight characteristics. Another disadvantage is that use of screws contributes to disk contamination. Particle generation occurs when the screws are driven for attaching the clamp.
Another type of disk clamp exists which does not require the use of screws to secure the clamp to the hub. Presumably, these types of clamps help to reduce undesirable radial or axial loading and also help to reduce contamination. One example of a clamping device which does not require the use of screws to secure a clamp to the hub includes the device disclosed in the U.S. Pat. No. 5,270,999. The disk clamp disclosed in this references has a flat lower surface which directly contacts the data disk. The central opening of the clamp includes an inner conical surface. The upper end of the hub includes a groove having a complementary conical surface. When the clamp is mounted over the hub, a uniform circumferential gap exists between the conical surfaces. A clip or spring is placed in the gap between the conical surfaces. When the spring is in place, the clamp resists axial force that may act to disengage the disk from the hub. The clamp disclosed in the ""999 patent provide very little axial force to secure the disk to the hub. Thus, the O-ring must be used to help prevent radial movement of the disk with respect to the hub. There is always some small gap between the inner edge of the disk defining the central opening and the outer surface of the hub. This gap can allow radial movement of the disk with respect to the hub if no force is provided to prevent such radial movement.
While the foregoing references may be adequate for their intended purposes, the clamp of the present invention further simplifies the overall disk clamp and hub arrangement, thus minimizing the cost of fabrication and assembly, reducing the likelihood of malfunction in the disk drive system, and providing effective and consistent performance.
In accordance with the preferred embodiment of the present invention, an apparatus in the form of a disk clamp, and a method for securing one or more data storage disks to a hub of a disk drive is provided. The disk clamp eliminates the need for using screws to secure the clamp to the hub. In use, the clamp provides an axial force upon the disk pack which prevents the disk(s) from both axial and radial displacement with respect to the hub. The axial force keeps the disk or disks from slipping relative to the hub during rotation, and during events such as high shock loads impacting the disk drive. The disk clamp is deflected by an external axial load, and then a retaining member such as a wire ring or multiple sections of wire arcs are inserted between an angled surface defining the central opening of the clamp and a corresponding sloping surface defining a concentric groove formed on the hub. Since screws are not used to set the clamp, uneven loads causing undesirable radial and axial forces upon the disk or disks are eliminated, thus reducing disk distortion in the direction of read/write flight. Furthermore, O-rings or other stabilizing structures are not required to stabilize the connection between the disk and the hub because of the axial force which is provided by the clamp.
The disk clamp includes a lower peripheral flange which contacts the underlying spacer or disk. When the external axial load is applied to set the clamp, the disk clamp itself acts as a spring in that it deflects downward in response to the applied axial load. After the retaining member is placed in the gap between the groove on the hub and the angled surface of the clamp, the axial load is removed which enables the disk clamp to spring back to its undeflected state; however, the retaining member prevents full return resulting in the retaining member being wedged between the clamp and the hub. A peripheral groove may be formed on the upper surface of the clamp for receiving a balance ring. The balance ring is sized and positioned to spin balance the disk pack.